The present technology relates to an analog-digital converter, solid-state image sensor, and electronic apparatus. In particular, the present technology relates to an analog-digital converter, solid-state image sensor, and electronic apparatus which can increase the resolution of AD conversion without trading off the processing time, the circuit area, or the like for the increased resolution and without degrading the image quality.
There have been provided solid-state image sensors, which convert an analog signal outputted from each pixel into a digital signal.
A solid-state image sensor typically has an AD conversion circuit disposed for each column therein. Signal voltages (analog signals) read from the floating diffusion (FD) of pixels arranged in a predetermined row of a pixel array are simultaneously converted into digital signals in respective columns.
Among the AD conversion methods, there has been often used a method called slope integration or ramp signal comparison. In this type, for example, a counting process is performed in parallel with a process of making a comparison between a ramp-shaped reference signal and an analog signal from a pixel; and at the point in time when the comparison process is complete, a digital signal is generated based on the counted value (for example, see Japanese Unexamined Patent Application Publication No. 2005-278135).
There is also an AD conversion method called successive approximation, in which a magnitude comparison is made between an analog signal from a pixel and a reference voltage using multiple capacitors to generate a digital signal.